1. Technical Field of the Invention
The present invention relates to stators for electric rotating machines that are used in, for example, motor vehicles as electric motors and electric generators, and to methods of manufacturing the stators.
2. Description of the Related Art
Conventionally, there are known stators for electric rotating machines which include a hollow cylindrical stator core and a stator coil.
The stator core has a plurality of slots that are formed in the radially inner surface of the stator core and spaced in the circumferential direction of the stator core. The stator coil is comprised of a plurality of electric wires mounted on the stator core. Each of the electric wires includes a plurality of in-slot portions, which are received in the slots of the stator core, and a plurality of turn portions that are located outside of the slots to connect the in-slot portions.
Moreover, there is disclosed, for example in Japanese Patent Application Publication No. 2001-145286, a method of manufacturing a stator. According to the method, to improve the space factors of the electric wires in the slots of the stator core, each of the electric wires forming U-phase, V-phase, and W-phase windings of the stator coil is configured to have a rectangular cross section and have such an overall shape that when developed on a plane, the electric wire meanders in the form of cranks. Further, the stator coil is formed by: (1) stacking a plurality of belt-shaped electric wires, which make up the U-phase, V-phase, and W-phase windings, to form a planar electric wire assembly; and (2) rolling the planar electric wire assembly by a predetermined number of turns into a hollow cylindrical shape.
For the thus-formed stator coil, it is necessary for those in-slot portions of the electric wires which are to be received in the same slot of the stator core to be aligned in a radial direction of the stator coil. However, due to springback of the electric wires which are only elastically deformed during the rolling step, it may be easy for misalignment between the corresponding in-slot portions of the electric wires to occur, rendering it difficult to keep the hollow cylindrical shape of the stator coil. Consequently, it may be difficult to easily and accurately assemble the stator coil with the stator core.